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Q. I’m on a low-carbohydrate diet to lose weight. I’d like to use meal replacement bars, but they contain something called glycerol. Is this a carbohydrate or not, and can I use it on my diet?

A. The popularity of low-carbohydrate diets means that many protein bars are now promoted as “low carb” foods. However, the debate about glycerol, one of the ingredients commonly included in protein bars, has left many people confused about whether protein bars can truly be considered low in carbs.

Glycerol (also known as glycerine) is a sweet-tasting, syrupy liquid used to sweeten as well as enhancing shelf life, moisture and mouth feel. Glycerol is classed as a carbohydrate mainly by default. It isn’t a protein, because there’s no nitrogen in it. Nor does it contain any fatty acids, so it can’t be called fat. Technically, glycerol (1,2,3- propanetriol) is a naturally occurring 3-carbon alcohol. The main benefit of glycerol is that it doesn’t affect insulin or blood sugar levels.

In a recent study, researchers compared a protein bar sweetened with glycerol with a protein bar sweetened with high fructose corn syrup. Compared to white bread, insulin levels after subjects ate the bar sweetened with glycerol were actually lower by about a quarter. However, insulin levels rose by more than one-third after participants ate the bar sweetened with high fructose corn syrup.

Look for a high-protein bar that contains sensible amounts of glycerol (such as Promax Meal bars or Cyclone bars by Maximuscle). Why? Too much glycerol can have a powerful laxative effect!